Various types of air bearings are currently used for moving loads over flat surfaces or for allowing the frictionless rotation of the component parts of a rotary or journal type bearing to rotate with respect to each other. U.S. Pat. Nos. 4,413,864 and 4,496,194 to Phillips disclose a gas bearing which has a spherically contoured pocket with a gas supply passage which opens in the center of the spherical pocket. The gas bearing is coupled to the load and is supported by a stem and ball joint through which the gas is supplied to the bearing. An additional passage allows gas to flow between the pocket and a closed chamber in the bearing. The separate chamber within the body of the gas bearing dampens the oscillations of the gas bearing. U.S. Pat. No. 3,186,774 to Wilcox indicates that if the thickness of the air cushion between a pair of relatively moving bearing members is limited to a specific thickness at one-half of the bearing load, the fluid friction of the air cushion will exceed the vibration energy generated by the dissipation of the gas energy in flowing between the two bearing members. A hydrostatic sliding element for moving over flat surfaces by means of a fluid which fills the gap between the movable elements is disclosed in U.S. Pat. No. 4,371,217 to Turza, et al. The hydrostatic sliding element has a sliding surface which is formed by three concentric rings which extend downwardly, and grooves between the rings and within the center of the innermost ring. Pressurized fluid is pumped into one of the grooves so that it then passes under the rings to lift the hydrostatic element. The outermost ring has radial grooves through which the pressurized fluid may escape into the outside environment. The rings create resistance to the escape of the pressurized fluid which tends to maintain the sliding surface of the hydrostatic element in proper balanced spaced relationship to the element over which it hovers.
An air bearing having a circular bearing surface with multiple spiral circulation ducts and an air supply duct is disclosed in U.S. Pat. No. 4,558,909 to Stauber. The air bearing also has a central bore for coupling the bearing body to a load base. The purpose of the spiral circulation ducts is to cause the pressurized air to be uniformly circulated over the bearing surface. U.S. Pat. No. 4,560,213 to Enderle, et al. discloses a gas bearing which has a circular flexible underside membrane. A hole in the center of the membrane serves as a gas-feed opening. As the air is forced through the bearing, the membrane assumes a conical shape. A hydrostatic bearing with a cylindrical recess in which is mounted a piston-like bearing pad and valve assembly is disclosed in U.S. Pat. No. 4,540,221 to Frazer.
U.S. Pat. Nos. 4,686,719 to Johnson, et al. and 4,528,704 to Wegener, et al. show semirigid air pallet-type patient movers which float on a cushion of air supplied by air escaping through small perforations. Rotary or journal-type fluid bearings are disclosed in U.S. Pat. Nos. 4,547,081 to Tanaka, et al., 4,542,994 to Mohsin, and 4,682,920 to Rogers. An oscillating pneumatodynamic bearing is disclosed in U.S. Pat. No. 4,666,315 to Scranton.
U.S. Pat. No. 3,272,568 to Koorneef, et al. discloses using magnets for urging the bearing surface toward a guide member over which the bearing surface is maintained in spaced relation.
Fluid bearings which move over flat support surfaces generally require a support surface which is stringently planar. If the air bearing surface which hovers over the support surface encounters an obstacle or a curved portion of the support surface, the air bearing surface is forced to rotate, thereby causing the entire air bearing to rotate and lose its parallel spaced relationship with the rest of the support surface. Such rotational action may destabilize the bearing. Portions of the air bearing surface may come into contact with the support surface, negating the substantially frictionless property of the bearing system.